1. Field of the Invention.
The invention relates generally to a machine tool for machining workpieces, and more particularly to machining with cutting tools and a laser beam.
2. Discussion of Related Art.
A machine tool of the general type that is relevant here is known from German patent publication 40 40 554. There, the laser beam is guided from a laser beam source mounted on the rear end of a spindle head in the axial direction of the spindle head through a hollow horizontal work spindle to a nozzle head insertable into the work spindle and provided with focusing optics. For a changeover from cutting to machining by means of a laser beam in such a machine tool, however, first a relatively complex exchange operation on the work spindle from a cutting tool to the nozzle head for laser machining is required.
It is a primary purpose of this invention to provide a machine tool of the above mentioned type enabling machining by means of cutting tools as well as machining by means of a laser beam with a simplified construction and without complex exchange operations.
According to the invention, the purpose is accomplished by disposing the beam guiding arrangement on the machining unit so as to be offset with respect to the work spindle.
The machine tool of the invention has the important advantage that laser beam machining may be carried out without the necessity of first inserting a nozzle head provided with focusing optics or the like into the work spindle. In addition, even conventional machine tools may be retrofitted for laser beam machining in a simple way due to the, for example, lateral arrangement of the beam guide on the machining unit.
Thus, in a particularly efficacious embodiment, the beam guiding arrangement comprises a laser head arranged laterally on a milling head and comprising a scanner system enabling a faster guidance of a focused laser beam across a predetermined machining area of the workpiece, for example, for cutting the material in layers. The machining area predetermined by the scanner system may be widened in a simple way without additional drives by the moving capacities of the milling head and the work table. Therefore, an enlarged area laser beam machining without any re-chucking of the workpieces is enabled.
For deflecting the laser beam for scanning the surface within the predetermined machining area, the scanner system efficaciously comprises a first deflection mirror turnable about the vertical axis and a second deflection mirror turnable about the horizontal axis. With the aid of slidable or adjustable focusing optics or plane field optics a displacement of the focusing position due to a distance change caused by a rotation of the deflection mirrors may be compensated in the path of the laser beam. By using focusing optics and plane field optics, an even more accurate correction may be obtained.
In another advantageous embodiment, the laser head, including the scanner system, is arranged on the milling head so that the beam emerges from the laser head below the front end of the work spindle. In this way, a small distance between the workpiece and the laser head may be selected. The laser head including the scanner system may be either fixedly or detachably held on the milling head. A detachable arrangement has the advantage that the machining area for cutting is not limited by the laser head and that the laser head may be moved to a protected storage position on a tool magazine or the like, for example, by means of an automatic tool exchanger, for protecting the scanner system while cutting is performed.